Personal computer (PC) applications (such as Instant Messenger) that allow a user to check for availability of users on a list of other users—applications called here “presence-enabled applications”—have become a success in the PC world. These kinds of applications, provided by a service (such as e.g. AMERICA ONLINE® Internet service provider) allow a PC user to create a list of other users—typically acquaintances of the user—who are also registered with the same service, and to then be informed when any of the other users become accessible (because of logging onto the service) or are no longer so. Furthermore, users are able to create status messages explaining more in detail their availability, and they can also exchange messages, files and other data via their lists.
Most of existing presence-enabled applications rely on the Internet and its IP-based address system. This enables presence features to work independently of physical location and distances. Thus, acquainted users can communicate (digitally) and be aware of each other's (digital) activities independent of their physical location.
On the other hand, this independence of physical location on the part of Internet-based presence applications via a PC actually limits or makes impossible certain usage modes users might consider desirable. For instance, Internet-based presence-enabled applications via a PC cannot indicate when a user is physically close to a buddy, thus suggesting a face-to-face rendezvous.
In a few countries, Internet-based Instant Messenger services are offered via mobile terminals. However unlike use of PC-based Instant Messenger, use on a mobile terminal often involves additional cost due to a required Internet connection via a mobile phone network.
A mobile form of presence-enabled application is offered by Presence-enhanced Contacts (PEC, also known as ‘Dynamic Contact Cards’), which imitates its PC-hosted internet-based counterpart by allowing a user to modify an availability indicator and to associate with it a text message (e.g. “Please call Mike. I am in a meeting.”) and/or a graphical element such as an image, which can be immediately accessed by subscribers of the same service via a phone book entry of the user. In a future version of PEC, it may also allow location information to be automatically and continually added to the published presence information and so made available to the selected subscribers of a user. In this way, subscribers to a user's presence information can know beforehand whether a user is available to accept a call or other communication, and if so how the user would prefer to be contacted, and if not, what other options are available.
Although mobile presence could potentially notify a user when another user is nearby, the constant polling of information (passive sharing) becomes cumbersome to set up, and further, is seen as undesirable by some users, for privacy reasons. Past user studies have indicated strong user rejection of automatically publishing location information of a user, for various reasons, including the fact that such location information is centrally stored on a server, accessible by the company providing the service (e.g. the operator) and can be disseminated to other users in the cellular network. Therefore the desirability of mobile presence-enabled application for providing presence information automatically is dubious.